Method for treatment of multiple sclerosis

ABSTRACT

Use of an A3 adenosine receptor agonist in the preparation of a pharmaceutical composition for the treatment of an individual suffering from multiple sclerosis. The composition is preferably orally administered. Also disclosed is a pharmaceutical composition for the treatment of multiple sclerosis that comprises an effective amount of an A3 adenosine receptor agonist and a pharmaceutically acceptable carrier.

FIELD OF THE INVENTION

This invention relates to compounds and methods useful in the treatmentof multiple sclerosis.

BACKGROUND OF THE INVENTION

Multiple sclerosis (MS) is a chronic, progressive, degenerative diseaseof the central nervous system (CNS), and particularly of the “whitematter” tissue. It is considered an autoimmune disease characterized byinflammation and demyelination of the CNS leading to chronic neuralgicdisturbances. Autoantibodies are generated by the immune system againstantigens of myelin proteins such as myelin basic protein (MBP) whichenvelops the spinal cord.

Experimental autoimmune encephalomyelitis (EAE) is the commonly usedanimal model for MS. It may be induced in wild-type animals such asrodents by inoculation, or appear spontaneously in geneticallysusceptible strains.

Adenosine receptors are classified into four major classes: A1, A2a, A2band A3. A3 adenosine receptors belong to the family of the G_(i)-proteinassociated cell surface receptors. Receptor activation leads to itsinternalization and the subsequent inhibition of adenylyl cyclaseactivity, cAMP formation and protein kinase A (PKA) expression,resulting in the initiation of various signaling pathways^((1,2)). PKAcontains a catalytic subunit PKAc which dissociates from the parentmolecule upon activation with cAMP.

U.S. Pat. No. 5,506,214 (Beutler) discloses treatment of patients havingMS with therapeutic agents containing substituted adenine derivativessuch as 2-chloro-2′-deoxyadenosine (CdA). Treatment with CdA was shownto markedly ameliorate the disease condition. CdA was found to be aputative partial agonist at A1 receptors, as described in Siddiqi, S. M.et al, (1995) J. Med. Chem. 38:1174-1188. The K_(i) values of CdA forthe various adenosine receptors were 7.4 μM at the A1 receptor, 20 μM atthe A2a receptor and 207 μM at the A3 receptor.

U.S. Patent Application No. 20020094974 (Castelhano, et al) disclosesnew N-6 substituted 7-deazapurine derivatives which are A3 adenosinereceptor antagonists. These compounds may be used for treating diseasesassociated with the A3 adenosine receptor, including neurologicaldisorders such as MS.

GENERAL DESCRIPTION OF THE INVENTION

The present invention is based on the surprising finding thatadministration of A3 adenosine receptor agonist (A3RAg) alleviatessymptoms of multiple sclerosis.

Thus, the present invention concerns, by one embodiment, a method forthe treatment of multiple sclerosis (MS) in a human subject, comprisingadministering to an individual in need of such treatment an effectiveamount of an A3RAg.

The term: “multiple sclerosis” (MS) refers in the context of the presentinvention to the inflammatory disease of the CNS in which the nerveinsulating myelin sheath is partially lost, resulting in variouspathological symptoms. MS includes various types of the disease such asrelapsing/remitting (RRMS), secondary progressive (SPMS), progressiverelapsing (PRMS) and primary progressive (PPMS).

The terms “treatment” or “neuralgic protection” in the context of thepresent invention refer to any improvement in the clinical symptoms ofthe disease, and/or a reduction in the rate of deterioration or therelapse rate of the MS patient, as well as any improvement in the wellbeing of the patients. For example, an improvement may be manifested byone or more of the following: decrease in muscle weakness, decrease inmuscle spasms, reduction of spasticity, improvement of balance andimprovement in memory.

The term “adenosine A3 receptor agonist” (A3RAg) in the context of thepresent invention refers to any molecule capable of specifically bindingto the adenosine A3 receptor (“A3R”), thereby fully or partiallyactivating said receptor. The A3RAg is thus a molecule that exerts itsprime effect through the binding and activation of the A3R. This meansthat at the doses it is being administered it essentially binds to andactivates only the A3R. In a preferred embodiment, an A3RAg has abinding affinity (K_(i)) to the human adenosine A3 receptor in the rangeof less than 100 nM, typically less than 50 nM, preferably less than 20nM, more preferably less than 10 nM and ideally less than 5 nM. Thelower the Ki, the lower the dose of the A3RAg (that may be used) thatwill be effective in activating the A3R and thus achieving a therapeuticeffect. Thus at times, A3RAgs that have a K_(i) to the human A3R of lessthan 2 nM and even less than 1 nM may be preferred.

It should be noted that some A3RAgs can also interact with and activateother receptors with lower affinities (namely a higher Ki). A moleculewill be considered an A3RAg in the context of the invention (namely amolecule that exerts its prime effect through the binding and activationA3R) if its affinity to the A3R is at least 3 times (i.e. its Ki to theA3R is at least 3 times lower), preferably 10 times, desirably 20 timesand most preferably at least 50 times larger than the affinity to anyother of the adenosine receptors (i.e. A1, A2a and A2b).

The affinity of an A3RAg to the human A3R as well as its relativeaffinity to the other human adenosine receptors (A1, A2a and A2b) can bedetermined by a number of assays, such as a binding assay. Examples ofbinding assays include providing membranes or cells having the receptorand measuring the ability of the A3RAg to displace a bound radioactiveagonist; utilizing cells that display the respective human adenosinereceptor and measuring, in a functional assay, the ability of the A3RAgto activate or deactivate, as the case may be, downstream signalingevents such as the effect on adenylate cyclase measured through increaseor decrease of the cAMP level; etc. Clearly, if the administered levelof an A3RAg is increased such that its blood level reaches a levelapproaching that of the Ki of the A1, A2a and A2b adenosine receptors,activation of these receptors may occur following such administration,in addition to activation of the A3R An A3RAg is thus preferablyadministered at a dose such that the blood level that will be attainedwill give rise to essentially only A3R activation.

The characteristic of some adenosine A3 receptor agonists and methods oftheir preparation are described in detail in, inter alia, U.S. Pat. No.5,688,774; U.S. Pat. No. 5,773,423, U.S. Pat. No. 5,573,772, U.S. Pat.No. 5,443,836, U.S. Pat. No. 6,048,865, WO 95/02604, WO 99/20284 and WO99/06053, WO 97/27173, all of which are incorporated herein byreference.

According to one embodiment of the invention, the A3RAg is a compoundthat exerts its prime effect through the binding and activation A3R andis a purine derivative falling within the scope of the general formula(I):

wherein,

-   -   R₁ represents an alkyl, hydroxyalkyl, carboxyalkyl or cyanoalkyl        or a group of the following general formula (II):

in which:

-   -   Y represents oxygen, sulfur or CH₂;    -   X₁ represents H, alkyl, R^(a)R^(b)NC(═O)— or HOR^(c)—, wherein        -   R^(a) and R^(b) may be the same or different and are            selected from the group consisting of hydrogen, alkyl,            amino, haloalkyl, aminoalkyl, BOC-aminoalkyl, and cycloalkyl            or are joined together to form a heterocyclic ring            containing two to five carbon atoms; and        -   R^(c) is selected from the group consisting of alkyl, amino,            haloalkyl, aminoalkyl, BOC-aminoalkyl, and cycloalkyl;    -   X₂ is H, hydroxyl, alkylamino, alkylamido or hydroxyalkyl;    -   X₃ and X₄ represent independently hydrogen, hydroxyl, amino,        amido, azido, halo, alkyl, alkoxy, carboxy, nitrilo, nitro,        trifluoro, aryl, alkaryl, thio, thioester, thioether, —OCOPh,        —OC(═S)OPh or both X₃ and X₄ are oxygens connected to >C═S to        form a 5-membered ring, or X₂ and X₃ form the ring of formula        (III):    -   where R′ and R″ represent independently an alkyl group;        -   R₂ is selected from the group consisting of hydrogen, halo,            alkylether, amino, hydrazido, alkylamino, alkoxy,            thioalkoxy, pyridylthio, alkenyl; alkynyl, thio, and            alkylthio; and        -   R₃ is a group of the formula —NR₄R₅ wherein        -   R₄ is a hydrogen atom or a group selected from alkyl,            substituted alkyl or aryl-NH—C(Z)—, with Z being O, S, or            NR^(a) with R^(a) having the above meanings; wherein when R₄            is hydrogen, then        -   R₅ is selected from the group consisting of R- and            S-1-phenylethyl, benzyl, phenylethyl or anilide groups            unsubstituted or substituted in one or more positions with a            substituent selected from the group consisting of alkyl,            amino, halo, haloalkyl, nitro, hydroxyl, acetoamido, alkoxy,            and sulfonic acid or a salt thereof; benzodioxanemethyl,            fururyl, L-propylalanyl-aminobenzyl, β-alanylamino-benzyl,            T-BOC-β-alanylaminobenzyl, phenylamino, carbamoyl, phenoxy            or cycloalkyl; or R₅ is a group of the following formula:

or when R₄ is an alkyl or aryl-NN—C(Z)—, then, R₅ is selected from thegroup consisting of heteroaryl-NR^(a)—C(Z)—, heteroaryl-C(Z)—,alkaryl-NR^(a)—C(Z)—, alkaryl-C(Z)—, aryl-NR—C(Z)— and aryl-C(Z)—; Zrepresenting an oxygen, sulfor or amine; or a physiologically acceptablesalt of the above compound.

According to one preferred embodiment, the A3RAg is a nucleosidederivative of the general formula (IV):

wherein X₁, R₂ and R₅ are as defined above, and physiologicallyacceptable salts of said compound.

The non-cyclic carbohydrate groups (e.g. alkyl, alkenyl, alkynyl,alkoxy, aralkyl, alkaryl, alkylamine, etc) forming part of thesubstituent of the compounds of the present invention are eitherbranched or unbranched, preferably containing from one or two to twelvecarbon atoms.

When referring to “physiologically acceptable salts” of the compoundsemployed by the present invention it is meant any non-toxic alkalimetal, alkaline earth metal, and ammonium salt commonly used in thepharmaceutical industry, including the sodium, potassium, lithium,calcium, magnesium, barium ammonium and protamine zinc salts, which areprepared by methods known in the art. The term also includes non-toxicacid addition salts, which are generally prepared by reacting thecompounds of this invention with a suitable organic or inorganic acid.The acid addition salts are those which retain the biologicaleffectiveness and qualitative properties of the free bases and which arenot toxic or otherwise undesirable. Examples include, inter alia, acidsderived from mineral acids, hydrochloric, hydrobromic, sulfuric, nitric,phosphoric, metaphosphoric and the like. Organic acids include, interalia, tartaric, acetic, propionic, citric, malic, malonic, lactic,fumaric, benzoic, cinnamic, mandelic, glycolic, gluconic, pyruvic,succinic salicylic and arylsulphonic, e.g. p-toluenesulphonic, acids.

Specific examples of A3RAg which may be employed according to generalformula (IV) of the present invention include, without being limitedthereto, N⁶-2-(4-aminophenyl)ethyladenosine (APNEA),N⁶-(4-amino-3-iodobenzyl) adenosine-5′-(N-methyluronanide) (AB-MECA),N⁶-(3-iodobenzyl)-adenosine-5′-N-methyluronamide (IB-MECA) and2-chloro-N⁶-(3-iodobenzyl)-adenosine-5′-N-methyluronamide (Cl-IB-MECA).

According to another embodiment, the A3RAg may be an oxide derivative ofadenosine, such as N⁶-benzyladenosine-5′-N-alkyluronamide-N¹-oxide orN⁶-benzyladenosine-5′-N-dialkyluronamide-N¹-oxide, wherein the 2-purineposition may be substituted with an alkoxy, amino, alkenyl, alkynyl orhalogen.

The administration of said A3RAg to a patient may be together with apharmaceutically acceptable carrier. In the case where theadministration is oral, the carrier is one that is acceptable for oraladministration.

By the term “pharmaceutically acceptable carrier” it is meant any one ofinert, non-toxic materials, which do not react with the A3RAg and whichcan be added to formulations as diluents or carriers or to give form orconsistency to the formulation. An oral formulation may be in the formof a pill, capsule, in the form of a syrup, an aromatic powder, andother various forms. The carrier is selected at times based on thedesired form of the formulation. The carrier may also at times have theeffect of the improving the delivery or penetration of the activeingredient to the target tissue, for improving the stability of thedrug, for slowing clearance rates, for imparting slow releaseproperties, for reducing undesired side effects etc. The carrier mayalso be a substance that stabilizes the formulation (e.g. apreservative), for providing the formulation with an edible flavor, etc.The carriers may be any of those conventionally used and is limited onlyby chemical-physical considerations, such as solubility and lack ofreactivity with the A3RAg, and by the route of administration. Thecarrier may include additives, colorants, diluents, buffering agents,disintegrating agents, moistening agents, preservatives, flavoringagents, and pharmacologically compatible carriers. In addition, thecarrier may be an adjuvant, which, by definition are substancesaffecting the action of the active ingredient in a predictable way.Typical examples of carriers include (a) liquid solutions, where aneffective amount of the active substance is dissolved in diluents, suchas water, saline, natural juices, alcohols, syrups, etc.; (b) capsules(e.g. the ordinary hard- or soft-shelled gelatin type containing, forexample, surfactants, lubricants, and inert fillers), tablets, lozenges(wherein the active substance is in a flavor, such as sucrose and acaciaor tragacanth or the active substance is in an inert base, such asgelatin and glycerin), and troches, each containing a predeterminedamount of the A3RAg as solids or granules; (c) powders; (d) suspensionsin an appropriate liquid; (e) suitable emulsions; (f) liposomeformulation; and others.

The term “effective amount” in the context of the present inventionrefers to an amount of A3RAg which results in neuralgic protection ofthe patient from the pathological symptoms of MS. The “effective amount”can be readily determined, in accordance with the invention, byadministering to a plurality of tested subjects various amounts of theA3RAg and then plotting the physiological response (for example anintegrated “MS index” combining several of the therapeuticallybeneficial effects) as a function of the amount. Alternatively, theeffective amount may also be determined, at times, through experimentsperformed in appropriate animal models and then extrapolating to humanbeings using one of a plurality of conversion methods; or by measuringthe plasma concentration or the area under the curve (AUC) of the plasmaconcentration over time and calculating the effective dose so as toyield a comparable plasma concentration or AUC. As known, the effectiveamount may depend on a variety of factors such as mode of administration(for example, oral administration may require a higher dose to achieve agiven plasma level or AUC than an intravenous administration); the age,weight, body surface area, gender, health condition and genetic factorsof the subject; other administered drugs; etc.

In the following, unless otherwise indicated, dosages are indicated inweight/Kg, meaning weight of administered A3RAg (e.g. IB-MECA orCl-IB-MECA) per kilogram of body weight of the treated subject in eachadministration. For example, mg/Kg and microgram/Kg denote,respectively, milligrams of administered agent and micrograms ofadministered agent per kilogram of body weight of the treated subject.

In mice the effective amount is typically less than about 1000 andpreferably less than about 500 microgram/Kg. A typical dose would be inthe range of about 1 microgram/Kg to about 200 microgram/Kg, with apreferred dose being in the range of about 5 microgram/Kg to about 150microgram/Kg. The corresponding effective amount in a human will be ahuman equivalent amount to that observed in mice, which may bedetermined in a manner as explained bellow.

The term “human equivalent” refers to the dose that produces in humanthe same effect as featured when a dose of 0.001-1 mg/Kg of an A3RAg isadministered to a mouse or a rat. As known, this dose depends and may bedetermined on the basis of a number of parameters such as body mass,body surface area, absorption rate of the active agent, clearance rateof the agent, rate of metabolism and others.

The human equivalent may be calculated based on a number of conversioncriteria as explained bellow; or may be a dose such that either theplasma level will be similar to that in a mouse following administrationat a dose as specified above; or a dose that yields a total exposure(namely area under the curve—AUC—of the plasma level of said agent as afunction of time) that is similar to that in mice at the specified doserange.

It is well known that an amount of X mg/Kg administered to rats can beconverted to an equivalent amount in another species (notably humans) bythe use of one of possible conversions equations well known in the art.Examples of conversion equations are as follows:

Conversion I: Species Body Wt. (Kg) Body Surf. Area (m²) Km Factor Mouse0.2 0.0066 3.0 Rat 0.15 0.025 5.9 Human Child 20.0 0.80 25 Adult 70.01.60 37

Body Surface area dependent Dose conversion: Rat (150 g) to Man (70 Kg)is 1/7 the rat dose. This means that, for example, 0.001-1 mg/Kg in ratsequals to about 0.14-140 microgram/Kg in humans. Assuming an averagehuman weight of 70 Kg, this would translate into an absolute dosage forhumans of about 0.01 to about 10 mg.

Conversion II:

The following conversion factors: Mouse=3, Rat=67. Multiply theconversion factor by the animal weight to go from mg/Kg to mg/m² forhuman dose equivalent. Species Weight (Kg) BSA (m²) Human 70.00 1.710Mouse 0.02 0.007 Rat 0.15 0.025 Dog 8.00 0.448

According to this equation the amounts equivalent to 0.001-1 mg/Kg inrats for humans are 0.16-64 μg/Kg; namely an absolute dose for a humanweighing about 70 Kg of about 0.011 to about 11 mg, similar to the rangeindicated in Conversion I.

Conversion III:

Another alternative for conversion is by setting the dose to yield thesame plasma level or AUC as that achieved following administration to ananimal. For example, based on measurement made in mice following oraladministration of IB-MECA and based on such measurements made in humansin a clinical study in which IB-MECA was given to healthy malevolunteers it can be concluded that a dose of 1 microgram/Kg-1,000microgram/KG in mice is equivalent to a human dose of about 0.14-140microgram/Kg, namely a total dose for a 70 Kg individual of 0.01-10 mg.

It should be noted that in addition to said therapeutic method, alsoencompassed within the present invention is a pharmaceutical compositionfor the treatment of multiple sclerosis that comprises an effectiveamount of an A3RAg as defined above and a pharmaceutically acceptablecarrier; as well as the use of said A3RAg for the preparation of apharmaceutical composition for administration to a subject sufferingfrom multiple sclerosis and being in need of a neuralgic protectivetreatment. As will be appreciated, the effective amount in thepharmaceutical composition will depend on the intended therapeuticregimen and the desired therapeutic dose. By way of example, where thedose is 1 mg per day and the. desired administration regimen is oncedaily, the amount of active agent in the pharmaceutical composition willbe 1 mg. In cases where it is intended to administer this daily dose in2 daily administrations, the amount of the active agent in thepharmaceutical composition will be 0.5 mg.

The invention will now be exemplified in the following description ofexperiments that were carried out in accordance with the invention. Itis to be understood that these examples are intended to be in the natureof illustration rather than of limitation. Obviously, many modificationsand variations of these examples are possible in light of the aboveteaching. It is therefore, to be understood that within the scope of theappended claims, the invention may be practiced otherwise, in a myriadof possible ways, than as specifically described hereinbelow.

BRIEF DESCRIPTION OF THE DRAWING

In order to understand the invention and to see how it may be carriedout in practice, a preferred embodiment will now be described, by way ofnon-limiting example only, with reference to the accompanying drawing,in which:

FIG. 1 is a graph illustrating the clinical symptoms of rats sufferingfrom EAE as a function of time, which were treated (□) or not treated(♦) with the A3RAg IB-MECA (CF101).

DETAILED DESCRIPTION OF THE INVENTION EXAMPLE I

Materials and Methods

IB-MECA, produced as a clinical grade material under clinical goodmanufacturing practice (cGMP) conditions by Albany Molecular Research,Albany, New York, USA on behalf of Can-Fite BioPharma, Ltd., Israel(this material is designated as CF101). A stock solution of 10 μM wasprepared in DMSO and further dilutions were made in RPMI medium.

Induction of Experimental Autoimmune Encephalomylitis (EAE)

EAE was induced by intradermal injection at the base of the tail offemale Lewis rats (8 weeks old) with an emulsion consisting of thefollowing for each rat: 100 μg myelin basic protein (MBP) from guineapig (M2295; Sigma), 0.1 ml Complete Freund's adjuvant (CFA; F5506,Sigma), and 0.2 mg of Mycobacterium tuberculosis H37 Ra (M.tuberculosis, 3114, Difco). The emulsion was injected in two halves intothe medial footpad of each hind limb of the rats. CF101 treatment PBSsolution (10 μg/kg, PO, BID (twice daily)) started at day 7 afterdisease induction. Control received PBS.

The rats developed clinical EAE symptoms which were graded into thefollowing categories: 0, no neurological symptoms; 1, loss of tail tonusand paralysis of the whole tail; 2, hind limbs weakness; 3, hind limbsparalysis; 4, quadriplegia; 5, moribund.

Results

The immunized rats developed acute monophasic EAE within 10 days afterimmunization that lasted for 5 days. A remarkably low clinical score inthe CF101 treated group in comparison to the control group was noted.The difference in the maximal clinical score between the CF101 and thecontrol groups was significant with P<0.01 using the Student's t test,and the severity of the disease in the treated group was significantlyreduced.

1-10. (canceled)
 11. A method for treating an individual suffering frommultiple sclerosis (MS) comprising administrating to said individual anA3 adenosine receptor agonist (A3RAg).
 12. The method of claim 11wherein said A3RAg is orally administered.
 13. The method of claim 11wherein said A3RAg is a compound within the scope of the general formula(I):

wherein, R₁ represents an alkyl, hydroxyalkyl, carboxyalkyl orcyanoalkyl or a group of the following general formula (II):

in which: Y represents an oxygen, sulfur or CH₂; X₁ represents H, alkyl,R^(a)R^(b)NC(═O)— or HOR^(c)—, wherein R^(a) and R^(b) may be the sameor different and are selected from the group consisting of hydrogen,alkyl, amino, haloalkyl, aminoalkyl, BOC-aminoalkyl, and cycloalkyl orare joined together to form a heterocyclic ring containing two to fivecarbon atoms; and R^(c) is selected from the group consisting of alkyl,amino, haloalkyl, aminoalkyl, BOC-aminoalkyl, and cycloalkyl; X₂ is H,hydroxyl, alkylamino, alkylamido or hydroxyalkyl; X₃ and X₄ representindependently hydrogen, hydroxyl, amino, amido, azido, halo, alkyl,alkoxy, carboxy, nitrilo, nitro, trifluoro, aryl, alkaryl, thio,thioester, thioether, —OCOPh, —OC(═S)OPh or both X₃ and X₄ are oxygensconnected to >C═S to form a 5-membered ring, or X₂ and X₃ form the ringof formula (III):

where R′ and R″ represent independently an alkyl group; R₂ is selectedfrom the group consisting of hydrogen, halo, alkylether, amino,hydrazido, alkylamino, alkoxy, thioalkoxy, pyridylthio, alkenyl;alkynyl, thio, and alkylthio; and R₃ is a group of the formula —NR₄R₅,wherein R₄ is a hydrogen atom or a group selected from alkyl,substituted alkyl or aryl-NH—C(Z)—, with Z being O, S, or NR^(a) withR^(a) having the above meanings; wherein when R₄ is hydrogen then R₅ isselected from the group consisting of R- and S-1-phenylethyl, benzyl,phenylethyl or anilide groups unsubstituted or substituted in one ormore positions with a substituent selected from the group consisting ofalkyl, amino, halo, haloalkyl, nitro, hydroxyl, acetoamido, alkoxy, andsulfonic acid or a salt thereof; benzodioxanemethyl, fururyl,L-propylalanyl-aminobenzyl, β-alanylamino-benzyl,T-BOC-β-alanylaminobenzyl, phenylamino, carbamoyl, phenoxy orcycloalkyl; or R₅ is a group of the following formula:

or when R₄ is an alkyl or aryl-NH—C(Z)—, then, R₅ is selected from thegroup consisting of heteroaryl-NR^(a)—C(Z)—, heteroaryl-C(Z)—,alkaryl-NR^(a)—C(Z)—, alkaryl-C(Z)—, aryl-NR—C(Z)— and aryl-C(Z)—, Zrepresenting an oxygen, sulfor or amine; or a physiologically acceptablesalt of the above compound.
 14. The method of claim 11 wherein saidA3RAg is a nucleoside derivative of the general formula (IV):

wherein, X₁ represents H, alkyl, R^(a)R^(b)NC(═O)— or HORC—, whereinR^(a) and R^(b) may be the same or different and are selected from thegroup consisting of hydrogen, alkyl, amino, haloalkyl, aminoalkyl,BOC-aminoalkyl, and cycloalkyl or are joined together to form aheterocyclic ring containing two to five carbon atoms; and R^(c) isselected from the group consisting of alkyl, amino, haloalkyl,aminoalkyl, BOC-aminoalkyl, and cycloalkyl; R₂ is selected from thegroup consisting of hydrogen, halo, alkylether, amino, hydrazido,alkylamino, alkoxy, thioalkoxy, pyridylthio, alkenyl; alkynyl, thio, andalkylthio; and R₅ is selected from the group consisting of R- andS-1-phenylethyl, benzyl, phenylethyl or anilide groups unsubstituted orsubstituted in one or more positions with a substituent selected fromthe group consisting of alkyl, amino, halo, haloalkyl, nitro, hydroxyl,acetoamido, alkoxy, and sulfonic acid or a salt thereof;benzodioxanemethyl, fururyl, L-propylalanyl-aminobenzyl,β-alanylamino-benzyl, T-BOC-β-alanylaminobenzyl, phenylamino, carbamoyl,phenoxy or cycloalkyl; or R₅ is a group of the following formula:

and physiologically acceptable salts of said nucleoside derivative. 15.The method of claim 11 wherein said A3RAg is selected fromN⁶-2-(4-aminophenyl)ethyladenosine (APNEA), N⁶-(4-amino-3-iodobenzyl)adenosine-5′-(N-methyluronamide) (AB-MECA), N-1-(3-iodobenzyl)-adenosine-5′-N-methyluronamide (IB-MECA) and2-chloro-N⁶-(3-iodobenzyl)-adenosine-5′-N-methyluronamide (Cl-IB-MECA).